1. Field of the Invention
The present invention relates to machine tools and, more particularly, to grinding and polishing tools for discs.
2. Description of the Prior Art
The computer industry employs rigid discs of various diameters for storage and retrieval of information encoded therein. The surfaces of these discs are scanned by close tolerance accurately positionable heads. The accuracy and density of the information storage and retrieval capability is a function of the degree of parallelism between opposed surfaces and the degree of finish on each surface. It is therefore very desirable to grind the discs to a high degree of parallelism between opposed sides, with each side being highly polished.
Various devices have been developed for truing the opposed sides of discs and grinding and polishing the respective surfaces. U.S. Pat. No. 3,845,587 is directed to a tool for spindle supporting each of a plurality of discs positioned intermediate extremely large sized and rigid grinding wheels. The opposed grinding wheels are dressed in situ and the grinding/polishing surfaces are maintained parallel to one another through employment of massive shafts, bearings and interconnecting framework. U.S. Pat. No. 1,656,820 is directed to a pair of grinding wheels having a vertically oriented axis of rotation. The upper grinding wheel rests upon the work piece being ground and the grinding force imparted thereto is a function of the weight of the grinding wheel and its spindle. U.S. Pat. No. 2,225,193 is directed to a grinding wheel having imbedded in the face thereof segmented abrasive elements. U.S. Pat. No. 2,371,021 is directed to a rotatable sanding or buffing tool which is preloaded. U.S. Pat. No. 2,826,877 is directed to a grinding and polishing element having a flexible intermediate member for preloading the grinding wheel. U.S. Pat. No. 3,676,957 is directed to apparatus for grinding helicoid springs. U.S. Pat. No. 3,668,812 is directed to a device for dressing the abrasive elements on a grinding wheel.